Use of materials incorporating microparticles for avoiding the proliferation of contaminants

ABSTRACT

A solid material including a matrix, dispersed in which are microparticles of at least one antimicrobial agent for preventing, limiting and/or eliminating the contamination of the material and/or the contamination of a composition which is in contact with the material for at least a given time, and/or preventing, eliminating and/or slowing down the formation of biofilms on the surface of the material, wherein the antimicrobial agent is an oxide of at least one positively charged metal ion and the antimicrobial agent does not migrate out of the material. Also, the use of such material for manufacturing an article, to the process for manufacturing the article, and to the article obtained. In particular, the article is selected from stoppers, lids, seals, caps, covers, plugs and valves intended for sealing bottles, flasks, jars, cans, canisters, barrels, tanks, or various containers used for packaging and/or storing food products, dietetic products, cosmetic products, dermatological products or pharmaceutical products.

INTRODUCTION

The present application relates to the use of a solid materialcomprising a matrix in which microparticles are dispersed, where thesaid particles have an antimicrobial effect. The application alsorelates to the use of the said material for the manufacture of anarticle, the method of manufacture of the said article, and the articlethat is obtained.

TECHNICAL FIELD

Repeatedly used compositions, in particular, those for cosmetic orpharmaceutical products, are subject to contamination risks as a resultof their exposure to: ambient air, and/or a means of application (anapplicator, a finger, etc.), and/or the organ for which the compositionis intended (for example, eye drops for an eye). Packaging, containersand/or delivery devices for such compositions may also be susceptible tocontamination.

To prevent and/or slow down the contamination of compositions, thestructure of the packaging, containers or delivery devices used for suchcompositions is generally designed to isolate the uncontaminated part ofthe composition from the part of the composition which is in contactwith ambient air, a means of application, an organ, and/or any otherpotential source of contamination. Thus, the containers designed tocontain compositions susceptible to be contaminated may include aphysical means of sealing, such as closing caps, valves and/or membranesallowing the isolation of the two parts of the composition from eachother. These containers require a specific and complicated manufacturingprocess, which increases the cost considerably. Moreover, even if suchsystems avoid the contamination of the part of the composition that hasbeen isolated, they do not necessarily avoid the contamination of thepart of the composition that is being delivered; for example, where anozzle being used to deliver the composition is itself contaminated.

Alternatively, the incorporation of organic or nanoscale antimicrobialagents in the materials that make up all, or parts of the packaging,containers, or delivery devices has also been explored. Thus, inparticular, plastic matrices comprising silver nanoparticles(nano-silver), zinc oxide nanoparticles or triclosan(5-chloro-2-(2,4-dichlorophenoxy)phenol), an organic biocide, have beenused in packaging, containers or delivery devices for compositionssusceptible to contamination. In particular, as a result of their size,these two types of agents (nano-objects and organic compounds) canmigrate and diffuse to a significant extent from the matrix into thecomposition. Such migration is undesirable. On the one hand, thismigration leads to “exhaustion” of the stock of antibacterial agentcontained in the matrix, which means that a large amount of the agentmust be incorporated to prevent the packaging, container, or dispenserdevice from losing its antibacterial properties. On the other, thepotential or actual toxicity of organic antibacterial agents andnano-objects discourages the use of compositions that contain them, inparticular, those to be used in the cosmetic and pharmaceutical sectors.Triclosan, in particular, has been identified as an endocrine disrupterin this respect. Zinc oxide nanoparticles, marketed as Zano® 20, byUmicore Zinc Chemicals are a typical example of the types ofnanoparticles used for incorporation into plastic matrices.

For compositions susceptible to contamination, it would be beneficial tohave the option of packaging, containers and/or delivery devices thatcan prevent and/or slow the contamination of the parts of compositionsthat are not in direct contact with sources of contamination(retro-contamination), the contamination of parts to be delivered, thecontamination of the packaging, and the contamination of containersand/or delivery devices, and also prevent the migration of anyantimicrobial agents incorporated into the packaging, containers and/ordelivery devices through compositions. These packaging materials,containers and/or delivery devices should preferably be of simplemechanical design, preferably identical to that used for compositionsnot susceptible to contamination, whose manufacture can be carried outsimply and inexpensively.

It is within this framework that the Applicant has demonstrated that theincorporation of specific microparticles into matrices, for example,polymeric matrices, allows antimicrobial properties to be imparted tothe materials obtained, without the antimicrobial agents being able tomigrate beyond the exterior of the material itself, in particular inapplications where a composition is in contact with the material. Thesematerials also allow the elimination and/or slowing of the formation ofbiofilms on the materials' surfaces. These materials can be used, inparticular, in the manufacture of packaging containers and deliverydevices for compositions susceptible to contamination.

SUMMARY OF THE INVENTION

A first object of the invention is the use of a solid materialcomprising a matrix and microparticles comprising or consisting of atleast one antimicrobial agent to prevent, limit and/or eliminatecontamination of the said material and/or the contamination of thecomposition that is in contact with this same material, for at least agiven time, and/or prevent, suppress and/or slow down biofilm formationon the surface of the said material, wherein the antimicrobial agentdoes not migrate out of the material.

A second object of the invention is the use of a solid materialcomprising a matrix and microparticles comprising or consisting of atleast one antimicrobial agent for the manufacture of an articlesusceptible to come into contact with at least one source of microbialcontamination, wherein the antimicrobial agent does not migrate out ofthe material or the article.

A further object of the invention is an article made of a materialcomprising a solid matrix and microparticles comprising or consisting ofat least one antimicrobial agent, wherein the article is susceptible tocome into contact with at least one source of microbial contaminationand wherein the antimicrobial agent does not migrate out of the materialor the article.

A final object of the invention is a manufacturing process for anarticle susceptible to come into contact with at least one source ofmicrobial contamination comprising a forming step of a solid materialcomprising a matrix and microparticles comprising or consisting of atleast one antimicrobial agent, wherein the antimicrobial agent does notmigrate out of the material or of the article.

BRIEF DESCRIPTION OF FIGURES

FIG. 1: Decrease in proliferation kinetics for a sample of materialaccording to the invention and for a control sample (Example 1).

FIG. 2: Evolution of bacterial growth as a function of preservativeconcentration for a control sample (a) and for a sample of materialaccording to the invention (b) (Example 2).

FIG. 3: Comparison of the antibacterial action of a control sample and amaterial sample according to the invention, depending on theconcentration of preservative (Example 2).

DETAILED DESCRIPTION OF THE INVENTION

A first object of the invention is the use of a solid materialcomprising a matrix and a set of microparticles comprising or consistingof at least one antimicrobial agent to prevent, limit and/or eliminatecontamination of the said material and/or the contamination of thecomposition that is in contact with the said material, for at least agiven time, and/or prevent, suppress and/or slow down biofilm formationon the surface of the said material, wherein the antimicrobial agentdoes not migrate out of the material.

The microparticles within the set of microparticles incorporated intothe material used according to the invention may be any type ofmicroparticles comprising or consisting of at least one antimicrobialagent. The preferred choice is spherical microparticles. The preferredchoice is for the entirety of the microparticles to be formed of a setof individualized microparticles, which are, preferably, uniformlydistributed in the matrix, particularly at the surface level of thematerial, which might be in contact with the source of contamination.

The invention also has the object of a process to prevent, limit and/oreliminate contamination of a material and/or the contamination of thecomposition that is in contact with this same material, for at least agiven time, and/or prevent, suppress and/or slow down biofilm formationon the surface of the said material, where the said process comprisesthe implementation or use of a solid material comprising a matrix and aset of microparticles, with the said microparticles comprising orconsisting of at least one antimicrobial agent. In particular, thematerial does not allow the said antimicrobial agent to migrate to theexterior of the said material.

In the present invention, “antimicrobial agent” means a substance thatkills, slows the growth of, or blocks the growth of, one or moremicrobes. In the present invention, “growth” means any cell operationthat leads to a volumetric increase in a cell, the division of a cell,or cell reproduction. In the present invention, “microbe” means anyunicellular or multicellular organism that is pathogenic or is parasiticto other organisms, such as humans. Microbes include moulds, fungi,yeasts, bacteria and viruses. An antimicrobial agent according to thepresent invention may be, for example, an agent that is antibiotic,fungicidal, fungistatic, bactericidal or bacteriostatic.

The terms fungicidal, fungistatic, bactericidal and bacteriostatic referto agents that are, respectively, able to remove at least one type ofmould, fungus or yeast, slow down the development of at least one typeof mould, fungus or yeast, eliminate at least one type of bacteria, orslow down the development of at least one type of bacteria. Thefungicide, fungistatic, bactericidal or bacteriostatic agent in theparticles used according to the invention may be selected by a skilledperson according to the conditions of use and the effect that is to beachieved.

The term bacterium refers to eubacteria and archaea. Eubacteria includefirmicutes, gracilicutes and tenericutes. Gracilicutes includegram-negative bacteria such as Enterobacteriaceae, examples of which areKlebsiella (as Klebsiella pneumoniae) and Escherichia (as Escherichiacoli). Fermicutes include gram-positive bacteria, such asMicrococcaceae, an example of which is Staphylococcus (such asStaphylococcus aureus), and stem-forming endospores including bacilli(Bacillaceae), for example, Bacillus circulans. All these references arementioned in Bergey's Manual of Systematic Bacteriology, Williams &Wilkens, 1st ed. Vol. 1-4, (1984).

The term “moulds” here includes fungi and yeasts.

The term “fungus” means any fungus or fungi present in an environment.The term fungus (fungi) includes Amastigomycota, such asDeuteromycotina, which includes Deuteromycetes. The Deuteromycetesinclude Aspergillus (Aspergillus niger) and Candida (Candida albicans).

For this invention, the term biofilm refers to a community ofmulticellular microorganisms (for example, bacteria, fungi, algae orprotozoa), which adhere to each other and to the surface of thematerial, and which are characterized by the secretion of an adhesiveand protective matrix.

In one embodiment, the particles are the particles of an oxide (forexample, a monoxide or a dioxide) of a positively charged metallic ion(M^(n+) where n is an integer between 1 and 4), especially those with adouble positive charge (M²⁺), and where, more specifically, the metaloxide is not an oxide of copper. For example, zinc oxide, magnesiumoxide, or titanium dioxide particles may be used, or a mixture or blendof such particles. In particular, it may be particles comprising amatrix of nanoparticles of such oxides that are used, in a matrix suchas an amorphous silica matrix.

In a particular embodiment, there are particles containing zinc oxide(ZnO) or comprising or consisting of magnesium oxide (MgO), orcomprising or consisting of a mixture of magnesium oxide and zinc oxide.In a more specific mode of carrying out the invention, the particlescomprise or consist of zinc oxide (ZnO).

These particles, containing zinc or magnesium oxide, or a mixture ofboth, may also contain titanium dioxide. Titanium dioxide can beincluded up to a maximum proportion of 10% by weight, and preferably amaximum of 5% by weight, and, in particular, a maximum of 2% by weight,relative to the total weight of particles.

The particles, particularly metal oxide particles, used according to theinvention can be doped with at least one chemical element known as adopant. The dopant should preferably be suitable to increase and/oroptimize the retarding properties of the metal oxide and/or theproperties that suppress the proliferation of contaminants, preferablythe fungicidal, fungistatic, bactericidal or bacteriostatic properties.For example, zinc oxide particles can be doped with at least onepositively charged ion (D^(m+), where m is an integer between 1 and 4),in particular, those of calcium, sodium, magnesium, titanium and/oraluminium.

The dopant is included up to a maximum concentration of 10% by weight,preferably a maximum of 5% by weight, and, in particular, a maximum of2% by weight.

The particles can include, in addition to the substance withantimicrobial properties, another compound having particular properties.For example, the particles may include an active ingredient, such as anessential oil.

In one embodiment, the microparticles are mesoporous particles,optionally encapsulating a compound having particular properties,preferably antimicrobial, such as an essential oil. In one embodiment,the mesoporous microparticles are particles of an oxide of a metallicion, as defined above, encapsulating a compound such as an essentialoil.

The particles included in the material used according to the inventionare microparticles, that is to say that their mean diameter (as aquantity) is between 0.1 and 1000 micrometres. In a particular mode ofthe invention, the particles have an average diameter of between 0.1 and5 micrometres, preferably between 0.4 and 5 micrometres, especiallybetween 0.5 and 3 or between 0.5 and 2 micrometres, in particular withan average diameter of about 0.5 micrometres. The skilled person knowsthe right techniques to be used to determine the value of the diameterof the particles, or aggregates of particles, according to theinvention. For example, the average diameter of the particles in a set,standard deviation and size distribution can be determined, inparticular, by statistical studies of microscopy images, for example,those generated by scanning electron microscopy (SEM) or transmissionelectron microscopy (TEM).

In this application, the term “about”, where it is used in relation to anumerical value, means an interval centred on this same numerical value,and ranging from 10% above its value to 10% below its value.

In this invention, a set of individualized particles refers to a set ofparticles wherein the particles are not aggregated; that is to say thateach particle in the set is not bound to any other particles by means ofa strong chemical bond, such as a covalent bond.

A set of particles used according to the invention may optionallycontain, on an ad hoc basis, particles that do not meet this criterion,provided the requirement for non-aggregation is complied with by atleast 50%, by number, of the total number of particles. Preferably, atleast 60%, at least 70%, at least 80%, at least 90%, and at least 95%,by number, of the particles of the set under consideration will beindividualized.

Preferably, a particle used according to the invention is not composedof an aggregate of several smaller particles. This can be clearlyanalysed by visual means, for example, by scanning electron microscopy(SEM) or transmission electron microscopy (TEM). This means that theonly possible constituents of the particles used according to theinvention are crystallites of a size significantly less than that of theparticles used according to the invention. A particle used according tothe invention is preferably formed of at least two crystallites. Acrystallite material is a type of material having the same structure asa single crystal; that is to say that within each atomic plane of itsstructure there are no major discontinuities of the crystalline orderwith the exception of point defects (vacancies or atoms inserted orsubstituted) or linear defects (dislocations).

Preferably, the particles used according to the invention areindividualized and not deformable. Also, the surface of each particlewhich is in contact with other particles is generally very weak. In oneembodiment, the radius of curvature of the meniscus forming the contactbetween two different particles of the set is less than 5%, preferablyless than 2%, of the radius of each of the two particles, especiallywithin a matrix used according to the invention.

The particles used according to the invention are spherical, inparticular, they have a sphericity coefficient greater than or equal to0.75. Preferably, the sphericity coefficient is greater than or equal to0.8, greater than or equal to 0.85, greater than or equal to 0.9, orgreater than or equal to 0.95.

The coefficient of sphericity of a particle is the ratio of the smallestdiameter of the particle to its largest diameter. For a perfect sphere,the ratio is 1. The sphericity coefficient can be calculated, forexample, by measuring the aspect ratio using any software adapted todeal with images, for example, images obtained by microscopy, inparticular, scanning electron microscopy (SEM) or transmission electronmicroscopy (TEM).

A set of particles used according to the invention may optionallycontain, on an ad hoc basis, particles that do not meet the criterion ofhaving the required sphericity, to the extent that the averagesphericity, as a quantity, of all the particles meets the criteriaset-out as part of the present invention. Preferably at least 50%, atleast 60%, at least 70%, at least 80%, at least 90%, and at least 95%,by number, of the particles of the set in question have a sphericity asdefined above.

The micrometric particles, in particular, those according to the sizesdefined above, have, more specifically, high specific areas. In aparticular embodiment, the particles of the invention have specificareas greater than or equal to 15 m²/g, preferably greater than or equalto 30 m²/g. The specific surface area of the particles according to theinvention can be up to 700 m²/g or 600 m²/g. Naturally, the specificsurface areas vary, particularly depending on the particle diameter andporosity. According to a particular mode of the invention, the meandiameter of the particles according to the invention is between 0.2 and5 micrometres and preferably between 0.4 and 3 micrometres, andexhibiting specific surface areas greater than or equal to 15 m²/g,preferably greater than or equal to 30 m²/g. The specific surface areascan be measured by various methods, especially the Brunauer, Emmett,Teller (BET) method or the Barrett, Joyner, Halenda (BJH) method. Thespecific surface area values given above are measured according to theBET method unless otherwise specified.

In a particular embodiment, the particles are as described in the Frenchpatent application filed on 7 May 2014 as application number FR 14 54141or PCT Patent Application No. PCT/ FR2015/ 051223 filed on 7 May 2015.

Individualized particles used according to the invention may be preparedby any method known to skilled workers in the field. In particular, theycan be prepared by the method described in the French patent applicationfiled on 7 May 2014 as application number FR 14 54141 or PCT PatentApplication No. PCT/ FR2015/ 051223 filed on 7 May 2015. Thisapplication describes a method of preparing a set of such particlesknown as “by aerosol pyrolysis” (or spray pyrolysis), which takes placeat drying temperatures and not necessarily pyrolysis temperatures. Inparticular, this method comprises the following successive steps:

-   -   (1) the nebulization of a liquid solution containing a precursor        to one or more inorganic material(s), from which the particles        are to be formed, at a given molar concentration in a solvent,        and which is used to obtain a spray of droplets of the solution,    -   (2) the heating of the spray (referred to as drying) to a        temperature sufficient to ensure the evaporation of the solvent        and the formation of particles,    -   (3) the heating of the particles to a temperature (referred to        as pyrolysis) sufficient to ensure the decomposition of the        precursor to form the inorganic material,    -   (4) optionally, the densification of the particles,    -   (4a) optionally, the quenching of the particles, and    -   (5) the recovery of the particles thus formed.

More specifically, the method for preparing a set of particles accordingto the invention is usually carried out in a reactor. The set ofparticles thus obtained may correspond to large quantities, morespecifically the amount obtained per day may be more than 100 g, 500 g,1 kg, 15 kg or 20 kg, with this amount varying according to the feedrate of solution to the reactor that occurs/ is required. The set ofparticles created therefore has the advantage of being obtained in largequantities while maintaining the particle characteristics describedabove. Step (1) of the nebulization is performed preferably at atemperature of 10 to 40° C., and/or preferably for a duration less thanor equal to 10 seconds, in particular, less than or equal to 5 seconds.In step (1), the liquid solution is generally in the form of an aqueousor hydroalcoholic solution or in the form of a colloidal sol. Morespecifically, the liquid solution in step (1) is introduced into areactor by nebulization.

Step (2), the heating (drying) step, is preferably carried out at atemperature of 40 to 120° C., and/or preferably for a time period lessthan or equal to 10 seconds, in particular between 1 and 10 seconds.

Step (3), referred to as pyrolysis, is preferably carried out at atemperature of 120 to 400° C., and/or preferably for a time period lessthan or equal to 30 seconds, in particular between 10 and 30 seconds.

Step (4), the optional densification, may be performed over a wide rangeof temperatures, especially between 200 and 1000° C. This step ispreferably carried out at a temperature of 400 to 1000° C., especiallywhen the particles that are to be prepared are at least partly incrystalline form. When seeking to obtain dense but non-crystallizedparticles, especially amorphous particles, densification temperature canbe lower, for example, it may be around 200° C. to 300° C., particularlyfor amorphous silica. Preferably, the densifying step is carried out fora duration less than or equal to 30 seconds, in particular between 20and 30 seconds.

Step (5), particle recovery, is preferably carried out at a temperaturebelow 100° C., and/or preferably for a period less than or equal to 10seconds, in particular, less than or equal to 5 seconds. Step (5),particle recovery, is preferably carried out by deposition of theparticles on a filter at the reactor outlet.

The temperature of each step may be outside the temperature ranges givenabove. For a given set of particles, the temperature to be applied candepend on the flow rate at which the drops and the particles circulatein the reactor. The more quickly the drops and the particles circulatein the reactor, the lower their residence time and higher thetemperature required in the reactor to achieve the same result.

Preferably, steps (2), (3) and (4) are carried out in the same reactor.In particular, all the steps in the method (except the post-processingsteps) are carried out in the same reactor.

The entirety of the steps in the method, especially steps (2), (3) and(4), are effected as a continuous sequence, one after the other. Thetemperature profile applied to the reactor is adapted as a function ofthe particles to be formed such that these three steps take place oneafter the other. Preferably, the temperature in the reactor is adjustedby means of at least one, and preferably three, heating elements, whosetemperatures can be set independently.

Moreover, the method for preparing a set of particles according to thepresent invention preferably comprises a step (4a) in which theparticles are quenched, which comes between step (3), or the optionalstep of particle densification (4), if there is to be one, and theparticle recovery step (5). The quenching step (4a) corresponds to arapid decrease in temperature. More specifically, if a particledensification step (4) is included, the quenching step is preferablycarried out, and advantageously involves a temperature decrease of atleast 300° C./s, in order to obtain, for example, a temperature between15 and 50° C. More specifically, if a particle densification step (4) isnot included, the quenching step may take place, and, if it takes place,it preferably corresponds to a temperature decrease of at least 100°C./s. The quenching step (4a) is preferably carried out by the input ofa gas, preferably cold air, to all or part of the circumference of thereactor. In the present invention, a gas is considered cold if it is ata temperature between 15 and 50° C., preferably between 15 and 30° C. Inone embodiment, the gas entering the reactor is a gas different fromair. In particular, it may be a neutral gas (such as nitrogen or argon),a reducing gas (such as hydrogen or carbon monoxide), or any mixture ofsuch gases.

The method for preparing a set of particles is carried out preferably inthe absence of a flow of gas that transports the spray from the inlet(for example, at the bottom) of the reactor. The laminar flow to carrythe material into the area with the highest temperature is best createdby the suction end only (for example, the top) of the reactor, producinga depression, for example of the order of several pascals or tens ofpascals.

Such an embodiment allows the use of a reactor without a gas inlet inits lower part, which limits process disturbances and losses, andmaximizes the efficiency of the process and the size distribution of theparticles obtained.

In another embodiment, the reactor in which the method is carried outalso comprises an inflow of gas at the level where the spray is formed.The gas entering the reactor at this level is preferably air, inparticular, hot air, that is to say at a temperature of 80 to 200° C.

Preferably, the method followed according to the invention does notinclude any further heating step in addition to those carried out withinthe aerosol pyrolysis reactor.

The precursor or precursors to the inorganic material(s) that is to beused to form the particles (in particular the metal oxides of positivelycharged ions, such as ZnO or MgO) may be of any origin. It (they) is(are) introduced in step (1) of the process as a liquid solution,especially an aqueous or hydroalcoholic solution containing the metalions (in particular an organic or inorganic salt of the chosen metal) oras precursor molecules (such as organosilanes) or in the form of acolloidal sol (as a colloidal dispersion of nanoparticles of the metalor the oxide of the chosen metal). Preferably, the precursor orprecursors to the inorganic materials is (are) introduced in step (1) ofthe process, as a liquid solution, especially an aqueous orhydroalcoholic solution containing the metal ions (such as an organic orinorganic salt of the chosen metal). The precursor(s) to the inorganicmaterials is (are) selected according to the type of particles to beformed.

The materials produced according to the invention have shown a highanti-contamination effectiveness despite the concentrations of particlesincorporated into the matrix being low. Anti-contamination effectivenesscan especially be measured according to the standard, ISO22196 (or JIS Z2801), which allows an antibacterial action for plastic and othernon-porous surfaces to be evaluated. Thus, in a particular aspect, thematerials produced according to the invention were tested using thisstandard and found to have antibacterial activity between 0 and 7CFU/cm², or between 1 and 7 CFU/cm², in particular between 2 and 7CFU/cm², and more particularly between 4 and 5.3 CFU/cm². The skilledperson will select the appropriate antimicrobial-activity criteriaaccording to the application.

Low concentrations of particles are known to help prevent particlemigration outside the material. The combination of anti-contaminationeffectiveness and the lack of particle release in the materials producedaccording to the invention may allow a reduction in the level ofpreservatives used, or even obviate the need for their use withincompositions, especially in food and/or pharmaceutical, dermatologicalor cosmetic products that are in contact with these materials. Toachieve the same rate of bacterial proliferation, it has beendemonstrated that using materials produced according to the inventionmakes it possible, under some conditions, to make a fourfold reductionin the level of preservatives in a composition in contact with theplastic matrix. The combination of anti-contamination effectiveness andthe lack of release of particles in materials developed according to theinvention may even allow the composition's expiry date to be delayed.The material properties of the invention can also be used to reduceradiation doses, for example, gamma radiation, which are used fordecontamination and/or sterilization of articles made with thesematerials. It is a well-known fact that sterilization by radiation hasdrawbacks. For example, it can contribute to discolouration and/orimpart an odour to a package and/or cosmetic composition.

The matrix used to prepare the material according to the invention isadvantageously a liquid matrix, whatever its viscosity, which allows theformation of a solid material that can be used according to theinvention, following the incorporation of the entirety of themicroparticles into the matrix, and, possibly following an additionaloptional step, such as a drying step. The characteristic “liquid” formof the matrix can be obtained by treating a non-liquid matrix; forexample, by heating it. The incorporation of the microparticles into thematrix is preferably carried out when the matrix is in liquid or moltenform; once the microparticles have been incorporated, the matrix issolidified in order to create a solid material.

Preferably, the matrix is an inorganic or organic matrix, for example, apolymeric matrix, especially a polymeric matrix of a plastic, rubber,varnish, paint, textile, silicone, glue, coating, or elastomer type. Ina particular aspect, the polymeric matrix consists of thermoplasticpolymers such as, in particular, acrylonitrile butadiene styrenecopolymer, cellulose acetate, polystyrene, especially expandedpolystyrene, polyamides, poly(butylene terephthalate), polycarbonates,high density polyethylene, low density polyethylene, poly(ethyleneterephthalate), poly(methyl methacrylate), polyformaldehyde,polypropylene, poly(vinyl acetate), poly(vinyl chloride), poly(lacticacid) (PLA), polycaprolactone, polyhydroxyalkanoate (PHA),polysaccharides, styrene-acrylonitrile copolymer, or a mixture of suchpolymers.

In a particular mode of the invention, the polymer matrix is a matrix ofa biopolymer; that is to say, a polymer derived from biomass, i.e.material produced by living organisms such as plants, algae, animals orfungi.

The matrix may also be a paint, an ink, or a matrix that is a precursorto a textile material or any material capable of forming films and/orcoatings on surfaces. Textile materials include, in particular,clothing, carpets, curtains, bedding and medical textile materials suchas bandages.

The proportion of microparticles distributed in the material may vary toa considerable extent depending on the nature of the particles and thematrix, and the intended use of the material and/or article. Preferably,the material or article of the invention comprises a low concentrationof particles with respect to the matrix, in particular of 0.1 to 10%, or0.1 to 5%, more specifically 0.5 to 3%, or 1 to 3% of the particles byweight relative to the total weight (the weight of the matrix and theparticles). As a strong preference, the material or article usedaccording to the invention contains about 0.2 to 2.5% by weight ofparticles relative to the total weight (the weight of the matrix and theparticles). A skilled person will be able to select the requiredproportion of particles in the material, in order to achieve the desiredanti-contamination effect, especially the antimicrobial effect, and tomaintain a release rate (in terms of particle migration outside of thematerial) that is as low as possible. The lower the concentration ofparticles in the material, the easier it becomes to maintain a lowparticle release rate. The materials used according to the inventionhave the characteristic of being able to maintain a very low (or zero)release rate, which corresponds to very low (or zero) particle migrationlevels, while, at the same time, the proportion of particles present issufficient to achieve a significant antimicrobial effect.

The material used according to the invention thus has the property ofsuppressing and/or slowing down proliferation of contaminants. Theseproperties are especially effective where the composition and/or theobject susceptible to be contaminated is placed in close contact withthe said material. In particular, the composition and/or the objectsusceptible to be contaminated is placed in contact with the material toslow and/or suppress the proliferation of contaminants.

In terms of effectiveness, the properties imparted to the material bythe inclusion of particles in the matrix, according to the invention,remain undiminished, or only slightly diminished, over time, as a resultof there being no transfer of the particles to the composition and/orthe object. For example, the bactericidal action of zinc oxide particlesis obtained by creation of reactive forms of oxygen, which, when theparticles are in contact with oxygen in the air, kill the bacteria.There is no consumption of the zinc oxide particles, only theconsumption of oxygen from the air or from the environment that thematerial is in.

In this invention, the fact that there is no migration of microparticlesoutside of the material, and, in particular, the fact that there is notransfer of the microparticles into the composition that is in contactwith the material, means that there is less than 1 mg of the mainelement making up the microparticles, preferably less than 0.5 mg, and,in particular, less than 0.01 mg, to be found in each kilogram of thecomposition. The main constituent making up the microparticles is ametal oxide, as defined above, in particular, magnesium oxide and/orzinc oxide.

In particular, this concentration can be measured by the method thatfollows, as recommended by the European Pharmacopoeia (for example:chapters 3.1.3 for polyolefins, 3.1.5 for polyethylenes, or 3.1.6 forpolypropylenes), where sample materials are first cut into pieces wherethe maximum length of any given side is 1 cm. 100 g of the materialdeveloped according to the invention and which is to be examined areintroduced into a borosilicate glass conical flask with a ground neck.20 mL of 0.1M hydrochloric acid are added. The mixture is heated underreflux for 1 hour with constant agitation. The solution is cooled toroom temperature (i.e., between 18 and 25° C.) and allowed to settle.The extractables are measured by atomic absorption spectrometry. Thetests enabled the measurement of a level of extractables of <1 ppm underthese test conditions with a polypropylene matrix (the extractable beingzinc, where the microparticles are based on ZnO).

Therefore, when the antimicrobial agent used according to the inventionis a metal oxide in the form of microparticles, the phrase “theantimicrobial agent does not migrate out of the said material” cancorrespond to a metal-ion migration rate that is less than or equal to50 ppm, to 25 ppm, in particular less than or equal to 10 ppm, or morespecifically less than 5 ppm (the lower limit generally being between 0and 1 ppm of the metal ion). The conditions under which these tests arecarried out are more severe than the typical conditions encountered bythe materials in normal use.

Of course, a migration rate outside of this range may be observed invery specific situations, especially when the material is placed inconditions that encourage degradation, for example, highly acidicconditions. However, such conditions are generally not found in food,cosmetic, dermatological or pharmaceutical applications.

Therefore, the materials used according to the invention retain theproperties that enable them to suppress and/or slow the proliferation ofcontaminants for a longer time, compared with materials containingantimicrobial agents which may migrate out of the material. Preferably,the material retains these properties for a period that is longer thanthe period for which the composition in contact with the material is tobe stored. In particular, the material retains these propertiesthroughout its life.

Preferably, the composition that is in contact with the material usedaccording to the invention is a food, dietary, cosmetic, dermatologicalor pharmaceutical composition. Preferably, it is a liquid, such as anophthalmic solution, a cream, such as a cosmetic or dermatologicalcream, a gel, or a food product. Thus, according to a particular aspectof the invention, the composition is a physiologically acceptablecomposition to a mammal, particularly a human, that is to say, it doesnot cause abnormal reactions or functions to occur in the said mammal;no safety issues have been detected for this physiologically acceptablecomposition.

The time during which the composition is in contact with the materialmay vary to a considerable extent. Thus, when the material is used tomanufacture a delivery device for a cosmetic lotion, the composition mayremain in contact with the material for several weeks, months, or evenyears. When the material is used to make or coat ducts conveying foodcompositions, the composition may remain in contact with the materialfor much shorter times, of the order of a minute or a second, or evenless than a second.

The use of a material developed according to the invention allows thecomposition that is contained in the article formed of the materialdeveloped according to the invention to be maintained in a clean state,that is to say, maintained free of any microbial contamination whoseorigin is its exposure, preferably its repeated exposure to ambient airand/or a means of application and/or the body for which the compositionis intended.

The term “repeated exposure” means that the article is used at leasttwice to supply at least a portion of the composition, and, therefore, apart of the composition remains in contact with the article after thefirst use.

In addition, the orifice for delivering the composition, for example,the end of the outlet of a pump or tube, remains clean despite itscontact with ambient air, the means of application and/or the body.Thus, there is no contamination of the part of the composition that willbe delivered via this orifice during the next use, unlike systemspresented previously, such as membrane systems or closing caps whoseorifices can be contaminated.

In the case of food products, the use of a container developed accordingto the invention makes it possible to limit microbial growth especiallyon the surface of the food product, thereby delaying, or eveneliminating the need for, a use-by-date whose determination usuallytakes into account the risk of bacterial growth.

Another object of the invention is the use of a material comprising amatrix and microparticles as defined above for the manufacturing of anarticle which may come into contact with at least one source ofmicrobial contamination.

For this invention, the phrase “source of microbial contamination” meansany part that may contain microbes and can transmit them to thematerial, the composition and/or article as they are defined in thepresent invention.

In one mode of carrying out the invention, the source of microbialcontamination arises from either ambient air, the means of application,such as a brush or a spatula, or an organ of a human or animal body.

Another object of the invention is a manufacturing process for anarticle susceptible to come into contact with at least one source ofmicrobial contamination, comprising a forming stage of a solid material,comprising a matrix and microparticles comprising or consisting of atleast one antimicrobial agent, such as that described above.

The manufacturing process may include a preliminary step to dispersemicroparticles in the matrix. This dispersion can be achieved by simplemixing, or optionally, by use of mechanical or magnetic stirring, orsonication.

The manufacturing process thus comprises a forming step for the article,using any technique known to a skilled worker and designed to effect theforming of the matrix and/or material. Thus, for example, in the case ofa polymeric matrix, the shaping step may be performed by injectionmoulding, injection stretch blow moulding, or extrusion blow moulding.

A further object of the invention is an article made of a solid materialcomprising a solid matrix and microparticles comprising or consisting ofat least one antimicrobial agent, as previously defined, where thearticle may come into contact with at least one source of microbialcontamination.

In one mode of carrying out the invention, the article forms all or partof the packaging, or a container or dispenser of a food, dietary,cosmetic, dermatological or pharmaceutical composition. The articledeveloped according to the invention may be either single use ormulti-use.

The article developed according to the invention is, in particular,likely to be selected from among the following: stoppers, seals,capsules, lids, plugs and taps for the closure of bottles, jars, pots,cans, barrels, tanks and various containers used for packaging and/orstorage of food, dietetic, cosmetic, dermatological or pharmaceuticalproducts.

Alternatively, the article may be all or a part of bottles, jars, pots,cans, barrels, tanks and various containers used for packaging and/orstorage of food, dietetic, cosmetic, dermatological or pharmaceuticalproducts.

In a preferred embodiment, the article is a container and/or a devicefor delivering a composition, particularly an ophthalmic solution, suchas eye drops or the products for contact lenses. Advantageously, it is asingle-use or multi-use bottle designed for pharmaceutical use. Forexample, a skilled person would be familiar with three-part ophthalmicproduct distribution devices. One, two, or all three of the three partsof the device can be produced with a material according to theinvention.

Among the articles suitable for storage and/or distribution ofpharmaceutical products, are spoons (such as spoons for syrup), syringes(such as syringes to administer, for example, a syrup), strips (such asstrips of tablets or capsules), bags (such as infusion bags), tubes,cannulas, pumps and bottles.

Among the articles suitable for storage and/or distribution of foodproducts, are trays, seals and packaging films.

Articles that may be in contact with sources of contamination include,in particular, piping, ductwork and work surfaces.

The various forms of packaging, containers or delivery devices of afood, dietary, cosmetic, dermatological or pharmaceutical compositionare well-known in the art. For example, delivery devices used for asolution generally comprise a substantial cylindrical moulded body(including oval bodies) having a bottom, a mouth or cannula, and aresealable closure, especially a screw cap, on the upper part.

A material or an article according to the invention can be used in awide variety of uses and fields. For example, such a material or articlecan be used to manufacture and/or coat the conduits carrying thecomponents likely to be contaminated, in particular, on an industrialsite. For example, the material, or the article, can be used to make theducts that transport the food, or food products, in a food processingplant. The use of a material or an article according to the inventionthen makes it possible to limit the formation of biofilms and thedevelopment and/or proliferation of germs. This allows the avoidance, ora reduction in the frequency, of washing ducts, which often involvesspecific techniques and requires isolation of the ducts for aconsiderable time, something that can affect the productivity of theplant. In addition, the use of articles or materials produced accordingto the invention allows the desired effect to be obtained over theentire surface, even in hidden areas or, for example, areas to whichaccess for the purpose of cleaning is difficult.

Similarly, articles and/or materials produced according to the inventioncan be used to manufacture equipment for any environment susceptible tocontamination, such as operating theatres, sterile rooms, surgicalinstrument environments or laboratory benches.

The following examples are included for illustrative purposes only anddo not limit the present invention.

EXAMPLES Example 1 Evaluation of the Antibacterial Effect of MaterialsProduced According to the Invention

The proliferation of different types of bacteria (Escherichia coli,Staphylococcus aureus, Pseudomonas aeruginosa, Listeria monocytogenes,Salmonella enterica, Staphylococcus epidermidis, Streptococcuspneumoniae and Haemophilus influenzae) was studied in samples ofmaterial produced according to the invention and compared with thatobserved for equivalent samples containing no particles. The tests wereconducted according to the standard, JIS Z 2801: 2010. The tests wereperformed in triplicate and the results shown below correspond to themean results for the three samples.

The bacterial strains Listeria monocytogenes and Salmonella enterica aretypically associated with the development of bacterial contamination infood products.

The bacterial strains Staphylococcus epidermidis, Streptococcuspneumoniae and Haemophilus influenzae are typically associated with thedevelopment of bacteria in the nasal area, and are therefore likely tobe present on any item that comes into contact with the face.

The sample of material produced according to the invention is a piece oflow density polyethylene (Purell PE 1840 H sold by the Lyondelbasellcompany) comprising spherical particles of zinc oxide of averagediameter 0.50 μm, with a specific surface area of about 15 m²/g,synthesized by the method described in patent application number FR 1454141. The concentration of spherical particles of zinc oxide is 2% byweight.

The control sample is also a piece of low density polyethylene plate(Purell PE 1840 H sold by the Lyondelbasell company).

The bacterial reference strains are the following: Escherichia coli CIP53126 and Staphylococcus aureus CIP 53156.

The sample pieces were treated with alcohol. The set of sample pieceswas then rinsed with sterile distilled water and dried under a laminarflow hood, prior to the tests being carried out. The covering film is asterile film made of Stomacher bags (40 mm×40 mm) (AES).

The suspensions were prepared with Nutrient Broth solution diluted to aconcentration of 1/500. The recovery solution is SCDLP solution asrecommended by the standard. Subsequent dilutions are carried out usingPBS (phosphate buffered saline). The medium is Trypticase soy agar(Biomerieux).

Depositions of amount 1.83×105 CFU (Colony Forming Units) were made onthe sample pieces. Proliferation is measured 24 hours after deposition,or one hour after the deposition (for Streptococcus pneumoniae andHaemophilus influenzae).

The results are shown in Table 1 below, the contamination value havingbeen normalized to 1 for the control sample (without particles).

TABLE 1 Proliferation for the sample of Proliferation material producedaccording for the Strain to the invention control sample Escherichiacoli 0.000628765 1 Staphylococcus aureus 0.009632989 1 Pseudomonas0.459916667 1 aeruginosa Listeria monocytogenes 6.21 × 10⁻⁵ 1 Salmonellaenterica 1.43 × 10⁻⁶ 1 Staphylococcus 0.011402338 1 epidermidisStreptococcus 0.41005694 1 pneumoniae Haemophilus influenzae 0.3007875341

Proliferation on the samples of material produced according to theinvention is significantly lower than for samples containing noparticles, for all types of bacteria tested.

The proliferation of bacteria was followed over a 24-hour test periodfor Escherichia coli. FIG. 1 shows the kinetics of the decrease inproliferation for the samples of material produced according to theinvention and for the control sample.

Other low density polyethylene samples (of Purell PE 1840 H sold by theLyondelbasell company) comprising spherical particles as specified abovecan be prepared, with particle concentrations ranging from 0.2 to 2.5%by weight.

Example 2 Study of the Influence of the Material Produced According tothe Invention on the Quantity of Preservatives Required

A quantity of the nutrient solution (Nutrient Broth) is deposited on asample of material produced according to the invention and on a controlsample as defined in Example 1. The dose of preservative (methylparaben)in the Nutrient Broth solution was varied, and the subsequent rate ofproliferation of Escherichia coli was compared under various conditionsafter 6 hours and after 24 hours of testing. The concentrations ofpreservative in solution are expressed as percentages by weight.

FIG. 2 shows the evolution of the growth of bacteria based onconcentrations of preservative for the control sample (a) and for thesample of material produced according to the invention (b).

FIG. 3 shows a comparison of antibacterial action, as a function ofpreservative concentration, for the control sample and the sample ofmaterial produced according to the invention.

Equivalent antibacterial activity is obtained for sample materialproduced according to the invention with 0.1% preservative solution, andfor the control sample with 0.4% preservative solution.

Therefore, compared with a composition in contact with a materialcontaining no particles, use of the material produced according to theinvention, when it is in contact with the same composition, can reducethe amount of preservative required by a factor of four.

Example 3 Retro-Contamination Study

This example relates to the evaluation of the treatment capacity of abottle of a product, such as eye drops, after simulated use for 14 daysand the regular application of potential contaminants of human origin(Staphylococcus aureus, Pseudomonas aeruginosa and Bacillus subtilis).

Materials and Methods

The following strains are used: Staphylococcus aureus CIP 4.83,Pseudomonas aeruginosa CIP 82118 and Bacillus subtilis (in spore form)CIP 52.62. Conservation and maintenance of the strains are carried outaccording to standard EN 12353 (September 2006). The stock bacterialsuspensions are made in accordance with the European Pharmacopoeia (7thedition, 2012, Chap. 2.6.12). Working suspensions are created from thestock solution by preparing six successive decimal dilutions in asterile suspension liquid containing 9 g/l of tryptone-salt(corresponding to a theoretical adjustment from 1.10² to 3.10² CFU/ml).The suspensions are counted using a plating method.

The control vial comprises the vial, end-piece and a polyethylene cap(Purell 1840H). The test vial comprises a vial, an end-piece, and a cap,of material made according to the invention (polyethylene of type Purell1840H containing spherical particles of ZnO of average diameter 500 nmand a specific surface area of about 15 m²/g). The vial, the end-pieceand the cap contain 2% by weight of spherical particles of ZnO.

The two vials are filled with 9 ml of 1/500 Nutrient Broth solution(containing 3 g meat extract, 10 g soy peptone, 5 g NaCl: quantitysufficient for 11). The pH is between 6.8 and 7.2. The protocol wasapplied to ten test vials and ten control vials.

For two weeks, eight simulations are performed at a rate of foursimulations a week on both types of vials. The simulation procedure isrepeated twice in a day.

The method of operation of the simulation procedure is:

-   -   Preparation of the working suspensions of the three        microorganisms as described above,    -   Preparation of an extemporaneous mixture of 10 ml containing the        three suspensions of equal volumes    -   Liberally soak a sterile swab with this suspension,    -   Unscrew the cap and remove a drop of product in the normal way,    -   Simulate use by applying the soaked swab to the product        distribution area, and    -   Screw the cap back on and store the vials at room temperature        until the next simulation.

The concentration of microorganisms present in the broth is assessedafter 7 days, and again after 14 days. After 14 days, the sterility ofthe broth is also checked in the control vial.

In terms of the count, the assay was performed according to therecommendations in Chapter 2.6.12 of the European Pharmacopoeia. Afterhomogenization of the contents of the vial by vortexing, 2×100 μLvolumes were added to a medium of Trypticase soy agar (Biomerieux)providing all the aerobic flora and Sabouraud (AES) providing all thefungal flora. The plates were incubated at 32.5±2.5° C. for 3 to 5 daysfor the Trypticase soy medium, and 22.5±2.5° C. for 5 to 7 days for theSabouraud medium.

Sterility evaluation tests were carried out according to therecommendations of Chapter 2.6.1 of the European Pharmacopoeia. It wascarried out only on the vials of material made according to theinvention and according to two modes of sampling.

For the vials numbered 1 to 5, the broth was collected after passagethrough the end-piece, in order to test it under the most unfavourableconditions.

For the vials numbered 6 to 10, the broth was collected directly fromthe inside of the vial, after unscrewing and taking off the end-piece.

The whole broth (about 8.5 ml) contained in different vials was sampledthen introduced into 100 ml of (Biomerieux) Trypticase soy broth.Incubation was carried out at 22.5±2.5° C. for 14 days. The observationof contamination indicates a positive test. In this case only, isolationwas carried out to allow identification of the contamination.

Two types of control were produced:

Negative Control:

A polyethylene vial containing 9 ml of broth was placed in the sameenvironmental conditions as the vials used in the test in order tovalidate the degree of sterility after 14 days of simulation.

Positive Control:

A polyethylene vial containing 9 ml of broth was inoculated with thethree bacteria (to a final concentration of about 3 CFU/ml) and placedunder the same ambient conditions as used in the tests in order toconfirm that the viability of microorganisms is maintained during the 14days of simulation.

Results

The results presented in the tables below are expressed in units of CFUper 100 microlitres of broth.

Enumeration

Table 2 below shows the results of enumeration at 7 and 14 days on theTrypticase soy agar medium. The vials of material produced according tothe invention are the “PE+ZnO” vials; the other vials (“PE” vials) arethe polyethylene control vials.

TABLE 2 7 days 14 days Sample PE vial PE + ZnO vial PE vial PE + ZnOvial No. 1   33** <1 >300** <1 No. 3    2** <1 >300** <1 No. 4   6*<1 >300** <1 No. 5    1** <1 >300**    2** No. 6 >300*  <1 >300** <1 No.7    1** <1 >300** <1 No. 8    1** <1 >300** <1 No. 9 >300**  <1 >300**<1 No. 10 >300**  <1 >300** <1 Negative <1  <1 <1 CPU <1 controlPositive control >300*  >300*  >300* >300* *Detection of Pseudomonasaeruginosa and Bacillus subtilis **Majority detection of Pseudomonasaeruginosa

Table 3 below shows the count results at 7 and 14 days on the Sabouraudmedium. The vials of material produced according to the invention arethe “PE+ZnO” vials; the other vials (“PE” vials) are the polyethylenecontrol vials.

TABLE 3 T7 days T14 days Sample PE vial PE + ZnO vial PE vial PE + ZnOvial No. 1 28 <1 >300 <1 No. 2 5 <1 >300 <1 No. 3 2 <1 >300 <1 No. 4 13<1 >300 <1 No. 5 1 <1 >300 1 No. 6 >300 <1 >300 <1 No. 7 1 <1 >300 <1No. 8 <1 <1 >300 <1 No. 9 >300 <1 >300 <1 No. 10 >300 <1 >300 <1Negative <1 <1 <1 <1 control Positive control >300 >300 >300 >300

The population observed on the Sabouraud agar is mainly bacterial inorigin (mainly Pseudomonas aeruginosa) except for polyethylene vial No.6, where the presence of moulds was detected in addition to thebacterial flora majority.

After 7 days of simulation, no vial of the 10 tested in the PE+ZnOseries (vials of material produced according to the invention) showedthe presence of contamination. At the same time, nine vials of the tentested in the PE series (the control vials) were contaminated, thecontamination level being heterogeneous from 1 CFU to 300 CFU detected.

After 14 days of simulation, a single vial of the ten tested in thePE+ZnO series (vials of material produced according to the invention)showed the presence of Pseudomonas aeruginosa. At the same time, allvials in the PE series (the control vials) were contaminated, showing ahigh degree of contamination of greater than 300 CFU per 100 μl ofbroth.

Evaluation of Sterility

Table 4 below summarizes the control sample sterility test results forthe vials produced according to the invention for which samples weretaken directly from inside the vial.

TABLE 4 Sample Growth Identification No. 6 Negative — No. 7 Negative —No. 8 Negative — No. 9 Negative — No. 10 Negative — Negative controlNegative — Positive control Positive Pseudomonas aeruginosaStaphylococcus aureus

The results demonstrate maintenance of sterile conditions in the brothfor the five vials where the samples were collected directly from insidethe container.

Conclusion

The use of a material produced according to the invention, for the vialand the end-piece, allows the risk of contamination of the broth underthe test conditions to be limited, namely artificial contamination ofthe end-piece, associated with a gram-positive bacterium (S. aureus), agram-negative bacterium (P. aeruginosa), and a gram negative bacteriumin spore form (Bacillus subtilis).

Under the same conditions, the use of polyethylene control vials ischaracterized by retro-contamination with significant growth of at leastone of the three contaminants.

Sterility controls carried out on the vials of material producedaccording to the invention confirm the absence of retro-contamination ofthe product contained in the package.

Example 4 Antimicrobial Activity Study

All the materials in the examples above (both inorganic and organicmaterials, such as plastic, rubber, varnish, paint, textile, silicone,glue, coatings, and elastomers) have been tested according to thestandard, ISO22196, and the results correspond to an antibacterialactivity in Escherichia coli samples of between 1 and 7 CFU/cm². Theconcentrations of particles by weight (with total weight comprising thematrix and the particles) are 0.2 to 2%, and the specific surface areasof the particles are 15 to 30 m²/g for an average particle diameter of0.50 μm.

The test described by the standard requires the use of three treatedsamples (40 mm×40 mm) and six untreated samples for each microorganismto be analysed.

-   -   A. Inoculation with a known concentration of the microorganism        to be tested, deposited homogeneously on the sample surface,    -   B. Determination of the concentration of viable microorganisms,        performed immediately after inoculation, and after 24 hours of        incubation of the culture, using the method based on the agar        medium,    -   C. The comparison of these counts allows determination of the        value of the antimicrobial activity on the surface analysed.

The test equipment is treated with alcohol. All test equipment is rinsedwith sterile distilled water and then dried under a laminar flow hoodprior to testing.

The sterile film is made from Stomacher bags (40 mm×40 mm).

Test conditions:

-   -   Contact temperature: 36±1° C.    -   Relative Humidity: 80%    -   Contact time: 24 hours

Results

For MgO particles:

MgO with a polyethylene matrix of low density RIBLENE (tests accordingto ISO22196 E. coli)

T0 control 1.38×10⁵ CFU

T0 sample: 1.44×10⁵ CFU

T24h control: 2.83×10⁷ CFU

T24h sample: 60 CFU

For particles of ZnO and MgO (quantities: 0.5% and 0.2% respectively byweight):

ZnO/MgO (weight ratio 2.5) with a low density polyethylene matrix ofPurell PE 1840 H (tests carried out according to ISO22196 E. coli)

T0 control 1.67×10⁵ CFU

T0 sample: 1.72×10⁵ CFU

T24h control 2.56×10⁷ CFU

T24h sample: 196 CFU

1. A method for preventing, limiting and/or eliminating contamination ofa solid material, and/or contamination of a composition that is incontact with said solid material, for at least a given time, and/or forpreventing, suppressing and or slowing-down biofilm formation on asurface of the said solid material, comprising forming a solid materialcomprising a matrix and a set of microparticles comprising or consistingof at least one antimicrobial agent, wherein the antimicrobial agent isa bactericidal or bacteriostatic agent which is an oxide of at least onepositively charged metal ion and where the antimicrobial agent does notmigrate out of the solid material.
 2. The method according to claim 1,wherein the concentration of the microparticles is 0.1 to 10%, or 0.1 to5%, more specifically 0.5 to 3%, or 1 to 3%, by weight, based on theweight of the matrix and particles.
 3. The method according to claim 1,wherein the microparticles have a mean diameter between 0.1 and 5micrometres, preferably between 0.4 and 5 micrometres.
 4. The methodaccording to claim 1; wherein the microparticles have specific areasgreater than or equal to 15 m²/g.
 5. The method according to claim 1,wherein the microparticles comprise zinc oxide or are constituted ofzinc oxide (ZnO), or comprise magnesium oxide or are constituted ofmagnesium oxide (MgO), or a mixture of magnesium oxide and zinc oxide.6. The method according to claim 5, wherein the microparticles areselected from ZnO microparticles, microparticles of ZnO doped withsodium or aluminium, and mesostructured microparticles comprising ZnO.7. The method according to claim 1; wherein the matrix is a polymericmatrix.
 8. The method according to claim 7, wherein the polymer matrixis a thermoplastic matrix polymer selected from acrylonitrile butadienestyrene copolymer, cellulose acetate, polystyrene, especially expandedpolystyrene, polyamides, poly(butylene terephthalate), thepolycarbonates, polyethylene, poly(ethylene terephthalate), poly(methylmethacrylate), polyformaldehyde, polypropylene, poly(vinyl acetate),poly(vinyl chloride), poly(lactic acid) (PLA), polycaprolactone,polyhydroxyalkanoate (PHA), polysaccharides and the copolymerstyrene-acrylonitrile.
 9. The method according to claim 1, wherein thecomposition is physiologically acceptable to a mammal and is preferablyselected from a food composition, a dietary composition, a cosmeticcomposition, a dermatological composition or a pharmaceuticalcomposition.
 10. (canceled)
 11. An article consisting of a solidmaterial comprising a matrix and a plurality of microparticlescomprising or consisting of at least one antimicrobial agent, whereinthe antimicrobial agent is a bactericidal or bacteriostatic agent whichis an oxide of at least one positively charged metal ion and where theantimicrobial agent does not migrate out of the solid material.
 12. Thearticle according to claim 11, wherein the article may be in contactwith at least one source of microbial contamination, and wherein theantimicrobial agent does not migrate outside of the material or thearticle.
 13. The article according to claim 11, wherein the article isused in a sterile environment, in an operating theatre, in a laboratory,or in the food industry.
 14. The article according to claim 11, whereinthe article is all or part of a package, container or delivery devicefor a food, dietary, cosmetic, dermatological or pharmaceuticalcomposition.
 15. The article according to claim 11, wherein the articleis selected from stoppers, seals, capsules, lids, plugs and taps for theclosure of bottles, jars, pots, cans, barrels, tanks and variouscontainers used for packaging and/or storage of food, dietetic,cosmetic, dermatological or pharmaceutical products.
 16. The articleaccording to claim 11, wherein the article forms all or part of bottles,flasks, jars, boxes, cans, barrels, tanks and various containers usedfor packaging and/or storage of food, dietetic, cosmetic, dermatologicalor pharmaceutical products.
 17. A method of making an article, where thesaid method comprises a step of forming a solid material comprising amatrix and a set of microparticles comprising or consisting of at leastone antimicrobial agent, wherein the antimicrobial agent is abactericidal or bacteriostatic agent which is an oxide of at least onepositively charged metal ion and where the antimicrobial agent does notmigrate out of the solid material.
 18. The method according to claim 17,further comprising a prior step of dispersion of the microparticles inthe matrix.
 19. A method of making the article according to claim 11,comprising adding to the article a solid material comprising a matrixand microparticles comprising or consisting of at least oneantimicrobial agent, wherein the article is susceptible to be in contactwith at least one source of microbial contamination, and theantimicrobial agent in the solid material is a bactericidal orbacteriostatic agent which is an oxide of at least one positivelycharged metal ion and where the antimicrobial agent does not migrate outof the solid material.